Charge director replenishment system and method for a liquid toner developing apparatus

Abstract

A system for imaging with liquid developer, the developer including carrier liquid, toner particles and charge director, the system including an electrostatic imaging surface apparatus for forming an electrostatic image on the electrostatic imaging surface, a reservoir for the liquid developer, a developer electrode for developing the electrostatic image with the liquid developer to form a developed image, apparatus for supplying the liquid developer to the electrostatic surface and for removing residual liquid developer from the developer electrode and returning the removed developer to the reservoir, apparatus for transferring the developed image to a substrate and charge director supply apparatus responsive to the charge level of the liquid developer, for supplying charge director at the developer electrode for maintaining the charge level of the liquid developer.

I claim: 
     
       1. A system for imaging with liquid developer, the liquid developer comprising carrier liquid, toner particles and charge director, the system comprising: an imaging surface having an electrostatic image formed thereon;   a reservoir for said liquid developer;   a developer electrode at least a portion of which is spaced from said imaging surface to form a development region therebetween;   a liquid developer supply system operative to supply liquid toner to said development region from the reservoir thereby to develop said electrostatic image;   means for transferring said developed image to a substrate; and   a charge director supply system which supplies charge director at said developer electrode responsive to the charge level of said liquid developer.   
     
     
       2. A system according to claim 1 and also including a liquid developer removal system operative to remove residual liquid developer from the developer electrode and return same to the reservoir. 
     
     
       3. A system according to claim 1 and also including a liquid developer removal system operative to remove residual liquid developer from the developer electrode and return same to the reservoir and to remove charge director which is supplied to the developer electrode, thereby maintaining the charge level of said liquid developer. 
     
     
       4. A system according to claim 1 wherein said developer electrode comprises: a rotating cylindrical developing electrode whose surface moves in adjacent spaced relationship to said imaging surface, and wherein   said charge director supply system supplies said charge director onto said developing electrode surface after it leaves the proximity of said imaging surface.   
     
     
       5. A system for imaging with liquid developer, the developer comprising carrier liquid, toner particles and charge director, the system comprising: an electrostatic imaging surface;   means for forming an electrostatic image to said electrostatic imaging surface;   a reservoir for said liquid developer;   a developer electrode for developing said electrostatic image with said liquid developer to form a developed image;   means for supplying said liquid developer to said electrostatic surface and for removing residual liquid developer from said developer electrode and returning said removed developer to said reservoir;   means for transferring said developed image to a substrate; and   charge director supply means responsive to the charge level of said liquid developer, for supplying charge director at said developer electrode for maintaining the charge level of said liquid developer.   
     
     
       6. A system according to claim 5 wherein said means for supplying directly delivers said liquid developer to said electrostatic imaging surface. 
     
     
       7. A system according to claim 6 wherein said means for removing is also operative to remove said charge director from said developer electrode for supplying said charge director to said reservoir. 
     
     
       8. A system according to claim 7 wherein said developer electrode comprises: a rotating cylindrical developing electrode whose surface moves in adjacent spaced relationship to said imaging surface, and   said means for supplying supplies said charge director onto said developing electrode surface after it leaves the proximity of said imaging surface.   
     
     
       9. A system according to claim 8 and wherein said means for removing comprises a plurality of single color cleaning assemblies for removing material including charge director supplied thereto from said developing electrode, each assembly corresponding to a given one of said liquid developers. 
     
     
       10. A system according to claim 9 and including means for supplying material removed by said cleaning assemblies from said developing electrode to its respective reservoir. 
     
     
       11. A system according to claim 6 wherein said developer electrode comprises: a rotating cylindrical developing electrode whose surface moves in adjacent spaced relationship to said imaging surface, and   said means for supplying supplies said charge director onto said developing electrode surface after it leaves the proximity of said imaging surface.   
     
     
       12. A system according to claim 11 and wherein said means for removing comprises a plurality of single color cleaning assemblies for removing material including charge director supplied thereto from said developing electrode, each assembly corresponding to a given one of said liquid developers. 
     
     
       13. A system according to claim 12 and including means for supplying material removed by said cleaning assemblies from said developing electrode to its respective reservoir. 
     
     
       14. A system according to claim 5 wherein said means for removing is also operative to remove said charge director from said developer electrode for supplying said charge director to said reservoir. 
     
     
       15. A system according to claim 14 wherein said developer electrode comprises: a rotating cylindrical developing electrode whose surface moves in adjacent spaced relationship to said imaging surface, and   said means for supplying supplies said charge director onto said developing electrode surface after it leaves the proximity of said imaging surface.   
     
     
       16. A system according to claim 15 and wherein said means for removing comprises a plurality of single color cleaning assemblies for removing material including charge director supplied thereto from said developing electrode, each assembly corresponding to a given one of said liquid developers. 
     
     
       17. A system according to claim 16 and including means for supplying material removed by said cleaning assemblies from said developing electrode to its respective reservoir. 
     
     
       18. A system according to claim 5 wherein said developer electrode comprises: a rotating cylindrical developing electrode whose surface moves in adjacent spaced relationship to said imaging surface, and   said means for supplying supplies said charge director onto said developing electrode surface after it leaves the proximity of said imaging surface.   
     
     
       19. A system according to claim 5 and wherein said means for removing comprises a plurality of single color cleaning assemblies for removing material including charge director supplied thereto from said developing electrode, each assembly corresponding to a given one of said liquid developers. 
     
     
       20. A system according to claim 19 and including means for supplying material removed by said cleaning assemblies from said developing electrode to its respective reservoir. 
     
     
       21. A method of imaging with liquid developer, the developer comprising carrier liquid, toner particles and charge director, the system comprising an imaging surface, a developer electrode at least a portion of which is closely spaced from the imaging surface to form a development region therebetween and a reservoir for said liquid developer, comprising the steps of: providing an electrostatic image on the electrostatic imaging surface;   providing liquid developer to the development region thereby to develop said electrostatic image; and   providing charge director at said developer electrode responsive to the charge level of said liquid developer.   
     
     
       22. A method according to claim 21 and also including the step of removing residual liquid developer from the developer electrode and returning same to the reservoir. 
     
     
       23. A method according to claim 22 wherein the step of removing also includes removing the charge director provided at the developer electrode and transferring same to the reservoir, thereby maintaining the charge level of the liquid developer.